(function() {
  d3.layout.arcDiagram = function() {
    var directed = true,
      size = [1,1],
      nodes = [],
      edges = [],
      edgeWeight = function (d) {return 1},
      nodeID = function (d) {return d.id};

    function arcDiagram() {
      var width = size[0],
      height = size[1],
      nodeStep = width / nodes.length,
      nodeHeight = height / nodes.length,
      constructedMatrix = [],
      matrix = [],
      edgeHash = {},
      nodeHash = {};

      nodes.forEach(function (node, i) {
        nodeHash[nodeID(node)] = node;
        node.x = i * nodeStep;
        node.y = size[1];
      })

      edges.forEach(function(edge) {
        if (typeof edge.source === "number") {
          edge.source = nodes[edge.source];
        }
        if (typeof edge.target === "number") {
          edge.target = nodes[edge.target];
        }
        var id = nodeID(edge.source) + "-" + nodeID(edge.target);

        if (!edgeHash[id]) {
          edgeHash[id] = edge;
        }
        else {
          edgeHash[id].weight = edgeHash[id].weight + edgeWeight(edge);
        }
      });

      return arcDiagram;
    }

    arcDiagram.directed = function(x) {
      if (!arguments.length) return directed;
      directed = x;
      return arcDiagram;
    }

    arcDiagram.size = function(x) {
      if (!arguments.length) return size;
      size = x;
      return arcDiagram;
    }

    arcDiagram.nodes = function(x) {
      if (!arguments.length) return nodes;
      nodes = x;
      return arcDiagram;
    }

    arcDiagram.links = function(x) {
      if (!arguments.length) return edges;
      edges = x;
      return arcDiagram;
    }

    arcDiagram.edgeWeight = function(x) {
      if (!arguments.length) return edgeWeight;
      if (typeof x === "function") {
        edgeWeight = x;
      }
      else {
        edgeWeight = function () {return x};
      }
      return arcDiagram;
    }

    arcDiagram.nodeID = function(x) {
      if (!arguments.length) return nodeID;
      if (typeof x === "function") {
        nodeID = x;
      }
      return arcDiagram;
    }

    arcDiagram.arc = function (d) {

        var draw = d3.svg.line().interpolate("basis");
        var midX = (d.source.x + d.target.x) / 2; //
        var midPercent = Math.abs(((d.source.x - d.target.x) / size[0]));

        var midY = size[1] + (midPercent * size[1]);
        if (d.source.x > d.target.x) {
          var midY = size[1] - (midPercent * size[1]);
        }

        return draw([[d.source.x,d.source.y],[midX,midY],[d.target.x,d.target.y]])
    }


    return arcDiagram;
  }

})();